This invention relates to centerless grinders, and more particularly relates to what is conventionally called the work rest or work rest assembly or work rest blade associated with centerless grinders and on which the work piece to be ground is supported during the grinding operation. Conventional centerless grinders incorporate a work rest blade assembly that includes a bar having a single surface on which the work piece is supported. Understandably, since a centerless grinder functions to grind off particles from the work piece being polished or ground, particles of the work piece and in many cases particles of the grinding wheels form a dust that collects between the work piece and the bar on which it is supported. Since such particles or dust is abrasive, and since the work piece is rotating in relation to the grinding wheels and in relation to the supporting bar, conventional work support bars have a very limited life. Accordingly, it is one of the objects of the present invention to provide a work rest blade assembly that may be used from four to six or more times as long as a conventional work support bar.
A centerless grinder functions to provide extremely accurate and highly polished surfaces on cylindrical objects. The accuracy with which the grinding is accomplished depends in large measure upon the condition of the grinding wheels and the work rest blade assembly associated therewith. In most instances, the accuracy with which a grinding operation is performed on a centerless grinder is dependent upon the competency of the individual operator. Since conventional work support bars in work rest blade assemblies wear rapidly because of the abrasive nature of the operation, a skilled operator must carefully reposition or adjust the work rest blade assembly and the work support bar carried thereby as grinding proceeds so as to compensate for any wear that might occur on the work support bar. The necessity for such adjustments introduces the possibility of inaccuracies which are reflected in the work piece. Accordingly, it is another object of the present invention to provide a work rest blade assembly including a work support bar which provides a multiplicity of unworn work support surfaces on which the work piece may be supported.
Another cause of inaccuracies in the grinding of a work piece in a centerless grinding machine is the tendency of the work support bar to vibrate. Such vibration changes the relationship between the work piece and the associated grinding wheels and as a consequence of the introduction of such variations in relationship inaccuracies appear in the surface being ground. The support bars included as a component of most conventional work rest support blade assemblies are generally rectangular in configuration and elongated and supported by opposite ends on opposite sides of the grinding wheels. This leaves the center of the support bar unsupported and subject to vertical and horizontal displacement in relation to its longitudinal axis as a result of the grinding forces imposed thereon. Accordingly, it is still another object of the invention to provide a work rest blade assembly incorporating a generally cylindrical work support bar which is supported over its entire length and which is tensioned on its surface next adjacent a work piece by imposition of a bending moment thereon so as to counteract any tendency of the support bar to move in relation to the work piece.
Still another object of the invention is to provide a generally cylindrical work support bar which is further tensioned by the imposition of rotary moments on opposite ends of the bar acting in opposite directions so as to twist the bar, thus further insuring the rigidity of the bar and its capability of withstanding vibrations without deleterious effect.
The invention possesses other objects and features of advantage, some of which with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.